Semiconductor device

ABSTRACT

According to one embodiment, a semiconductor device includes first to third electrodes, first and second semiconductor regions, a first insulating member, and a nitride member. The third electrode includes a first electrode portion. A position of the first electrode portion is between a position of the first electrode and a position of the second electrode. The first semiconductor region includes first to fifth partial regions. A position of the fourth partial region is between positions of the first and third partial regions. A position of the fifth partial region is between positions of the third and second partial regions. The second semiconductor region includes first and second semiconductor portions. The first electrode portion is located between the first and second semiconductor portions. The first insulating member includes first to third insulating regions. The nitride member includes first to third nitride regions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No.2022-017621, filed on Feb. 8, 2022; theentire contents of which are incorporated herein by reference.

FIELD

Embodiments of the invention generally relate to a semiconductor device.

BACKGROUND

For example, there is a semiconductor device using a nitridesemiconductor. It is desired to improve the characteristics ofsemiconductor devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view illustrating a semiconductordevice according to a first embodiment;

FIGS. 2A to 2D are images illustrating analysis results of thesemiconductor device according to the first embodiment;

FIGS. 3A to 3D are images illustrating analysis results of thesemiconductor device according to the first embodiment;

FIGS. 4A and 4B are graphs illustrating analysis results of thesemiconductor device in the first embodiment;

FIGS. 5A and 5B are graphs illustrating analysis results of thesemiconductor device in the first embodiment; and

FIG. 6 is a schematic cross-sectional view illustrating a semiconductordevice according to the first embodiment.

DETAILED DESCRIPTION

According to one embodiment, a semiconductor device includes a firstelectrode, a second electrode, a third electrode, a first semiconductorregion, a second semiconductor region, a first insulating member, and anitride member. The third electrode includes a first electrode portion.A position of the first electrode portion in a first direction from thefirst electrode to the second electrode is between a position of thefirst electrode in the first direction and a position of the secondelectrode in the first direction. The first semiconductor regionincludes Al_(x1)Ga_(1-x1)N (0 ≤ x1 < 1). The first semiconductor regionincludes a first partial region, a second partial region, a thirdpartial region, a fourth partial region, and a fifth partial region. Adirection from the first partial region to the first electrode is alonga second direction crossing the first direction. A direction from thesecond partial region to the second electrode is along the seconddirection. A direction from the third partial region to the firstelectrode portion is along the second direction. A position of thefourth partial region in the first direction is between a position ofthe first partial region in the first direction and a position of thethird partial region in the first direction. A position of the fifthpartial region in the first direction is between the position of thethird partial region in the first direction and a position of the secondpartial region in the first direction. The second semiconductor regionincludes Al_(x2)Ga_(1-x2)N (0 < x2 ≤ 1, x1 < x2). The secondsemiconductor region includes a first semiconductor portion and a secondsemiconductor portion. The first electrode portion is located betweenthe first semiconductor portion and the second semiconductor portion inthe first direction. A direction from the fourth partial region to thefirst semiconductor portion is along the second direction. A directionfrom the fifth partial region to the second semiconductor portion isalong the second direction. The first insulating member includes a firstinsulating region, a second insulating region, and a third insulatingregion. The first insulating region is located between the third partialregion and the first electrode portion in the second direction. Thesecond insulating region is located between the first semiconductorportion and the first electrode portion in the first direction. Thethird insulating region is located between the first electrode portionand the second semiconductor portion in the first direction. The nitridemember includes a first nitride region, a second nitride region and athird nitride region. The first nitride region is located between thethird partial region and the first insulating region in the seconddirection. The second nitride region is located between the firstsemiconductor portion and the second insulating region in the firstdirection. The third nitride region is located between the thirdinsulating region and the second semiconductor portion in the firstdirection. The first nitride region includes Al_(z1)Ga_(1-z1)N (0 < z1 <1, x1 < z1). The second nitride region includes Ai_(z2)Ga_(1-z2)N (0 <z2 ≤ 1, z1 < z2).

Various embodiments are described below with reference to theaccompanying drawings.

The drawings are schematic and conceptual; and the relationships betweenthe thickness and width of portions, the proportions of sizes amongportions, etc., are not necessarily the same as the actual values. Thedimensions and proportions may be illustrated differently amongdrawings, even for identical portions.

In the specification and drawings, components similar to those describedpreviously in an antecedent drawing are marked with like referencenumerals, and a detailed description is omitted as appropriate.

First Embodiment

FIG. 1 is a schematic cross-sectional view illustrating a semiconductordevice according to the first embodiment.

As shown in FIG. 1 , a semiconductor device 110 according to theembodiment includes a first electrode 51, a second electrode 52, a thirdelectrode 53, a first semiconductor region 11, a second semiconductorregion 12, a first insulating member 41, and a nitride. Includes member31.

A direction from the first electrode 51 to the second electrode 52 isdefined as a first direction D1. The first direction D1 is, for example,an X-axis direction. One direction perpendicular to the X-axis directionis defined as a Z-axis direction. The direction perpendicular to theX-axis direction and the Z-axis direction is defined as a Y-axisdirection. For example, the first to third electrodes 51 to 53 mayextend in the Y-axis direction.

The third electrode 53 includes a first electrode portion 53 a. Aposition of the first electrode portion 53 a in the first direction D1is between a position of the first electrode 51 in the first directionD1 and a position of the second electrode 52 in the first direction D1.

The first semiconductor region 11 includes Al_(x1)Ga_(1-x1)N (0 ≤ x1 <1). The first semiconductor region 11 includes, for example, GaN. Thecomposition ratio x1 is, for example, not less than 0 and less than 0.1.

The first semiconductor region 11 includes a first partial region 11 a,a second partial region 11 b, a third partial region 11 c, a fourthpartial region 11 d, and a fifth partial region 11 e. A direction fromthe first partial region 11 a to the first electrode 51 is along asecond direction D2. The second direction D2 crosses the first directionD1. The second direction D2 is, for example, the Z-axis direction. Thesecond direction D2 may be perpendicular to the first direction D1.

A direction from the second partial region 11 b to the second electrode52 is along the second direction D2. A direction from the third partialregion 11 c to the first electrode portion 53 a is along the seconddirection D2. A position of the fourth partial region 11 d in the firstdirection D1 is between a position of the first partial region 11 a inthe first direction D1 and a position of the third partial region 11 cin the first direction D1. A position of the fifth partial region 11 ein the first direction D1 is between the position of the third partialregion 11 c in the first direction D1 and a position of the secondpartial region 11 b in the first direction D1. The boundaries betweenthe first to fifth partial regions 11 a to 11 e may be unclear. Thesepartial regions may be contiguous with each other.

The second semiconductor region 12 includes Al_(x2)Ga_(1-x2)N (0 < x2≤1, x1 < x2). The second semiconductor region 12 includes, for example,AlGaN. The composition ratio x2 is, for example, not less than 0.1 andnot more than 1. The composition ratio x2 may be, for example, not lessthan 0.1 and not more than 0.5.

The second semiconductor region 12 includes a first semiconductorportion 12 a and a second semiconductor portion 12 b. The firstelectrode portion 53 a is located between the first semiconductorportion 12 a and the second semiconductor portion 12 b in the firstdirection D1. A direction from the fourth partial region 11 d to thefirst semiconductor portion 12 a is along the second direction D2. Adirection from the fifth partial region 11 e to the second semiconductorportion 12 b is along the second direction D2.

The first insulating member 41 includes a first insulating region 41 a,a second insulating region 41 b, and a third insulating region 41 c. Thefirst insulating region 41 a is located between the third partial region11 c and the first electrode portion 53 a in the second direction D2.The second insulating region 41 b is located between the firstsemiconductor portion 12 a and the first electrode portion 53 a in thefirst direction D1. The third insulating region 41 c is located betweenthe first electrode portion 53 a and the second semiconductor portion 12b in the first direction D1. The boundaries between the first to thirdinsulating regions 41 a to 41 c may be unclear. These insulating regionsmay be continuous with each other.

The nitride member 31 includes a first nitride region 31 a, a secondnitride region 31 b, and a third nitride region 31 c. The first nitrideregion 31 a is located between the third partial region 11 c and thefirst insulating region 41 a in the second direction D2. The secondnitride region 31 b is located between the first semiconductor portion12 a and the second insulating region 41 b in the first direction D1.The third nitride region 31 c is located between the third insulatingregion 41 c and the second semiconductor portion 12 b in the firstdirection D1. The boundaries between the first to third nitride regions31 a to 31 c may be unclear. These nitride regions may be continuouswith each other.

The first nitride region 31 a includes Al_(z1)Ga_(1-z1)N (0 < z1 < 1, x1< z1). The second nitride region 31 b includes Al_(z2)Ga_(1-z2)N (0 <z2≤ 1, z1 < z2). Thus, regions having different Al composition ratio areprovided in the first nitride member 31. In one example, the secondnitride region 31 b includes AIN. The first nitride region 31 a includesAlGaN. For example, the composition ratio z2 may be higher than thecomposition ratio x2.

The first semiconductor region 11 and the second semiconductor region 12are included in a semiconductor member 10 M. The semiconductor device110 may include a base body 10S and a nitride layer 10B. The base body10S may include, for example, a silicon substrate, a GaN substrate, aSiC substrate, or the like. The nitride layer 10B may include a nitridesemiconductor. The nitride layer 10B is, for example, a buffer layer.The nitride layer 10B is provided on the base body 10S. Thesemiconductor member 10 M is provided on the nitride layer 10B. Thefirst to third electrodes 51 to 53 are provided on the semiconductormember 10 M.

The first electrode 51 is electrically connected with the firstsemiconductor portion 12 a. The second electrode 52 is electricallyconnected with the second semiconductor portion 12 b.

A current flowing between the first electrode 51 and the secondelectrode 52 can be controlled by a potential of the third electrode 53.The potential of the third electrode 53 may be, for example, a potentialbased on a potential of the first electrode 51. The first electrode 51functions as, for example, a source electrode. The second electrode 52functions as, for example, a drain electrode. The third electrode 53functions as, for example, a gate electrode. The semiconductor device110 is a transistor.

A carrier region 10 c is formed in a portion of the first semiconductorregion 11 facing the second semiconductor region 12. The carrier region10 c is, for example, a two-dimensional electron gas. The semiconductordevice 110 is, for example, a HEMT (High Electron Mobility Transistor).

As described above, the first electrode portion 53 a of the thirdelectrode 53 is located between the first semiconductor portion 12 a andthe second semiconductor portion 12 b in the first direction D1. Asshown in FIG. 1 , a part of the first electrode portion 53 a may belocated between the fourth partial region 11 d and the fifth partialregion 11 e in the first direction D1. The third electrode 53 is, forexample, a recess type gate electrode. Thereby, a high threshold isobtained. For example, a normally-off operation can be obtained.

In the embodiment, as described above, the composition ratio isdifferent between the first nitride region 31 a provided at the bottomof the recess and the second nitride region 31 b provided at the side ofthe recess. The composition ratio of Al in the first nitride region 31 ais lower than the composition ratio of Al in the second nitride region31 b. This suppresses excessive carrier formation at the bottom of therecess.

If the carrier concentration becomes excessively high at the bottom ofthe recess, for example, a short channel effect occurs. This may causethe threshold voltage to decrease excessively. In the embodiment,excessively high carrier concentration is suppressed at the bottom ofthe recess. As a result, the threshold voltage can be stably controlledto the target voltage. For example, high channel mobility is maintained.High carrier mobility and stable high threshold voltage can be obtained.According to the embodiment, it is possible to provide a semiconductordevice whose characteristics can be improved.

In the semiconductor device 110, the third nitride region 31 c includesAl_(z3)Ga_(1-z3)N (0 < z3 ≤ 1, z1 < z3). The third nitride region 31 cincludes AIN, for example. In the embodiment, the composition ratio ofAl in the nitride regions (the second nitride region 31 b and the thirdnitride region 31 c) of the two sides may be higher than the compositionratio of Al in the first nitride region 31 a. For example, thecomposition ratio z3 may be higher than the composition ratio x2.

In the embodiment, the first insulating member 41 includes silicon andoxygen. The first insulating member 41 includes, for example, SiO₂.

As shown in FIG. 1 , the semiconductor device 110 may further include asecond insulating member 42. The second insulating member 42 includes afirst insulating portion 42 a and a second insulating portion 42 b. Thefirst semiconductor portion 12 a is located between the fourth partialregion 11 d and the first insulating portion 42 a in the seconddirection D2. The second semiconductor portion 12 b is located betweenthe fifth partial region 11 e and the second insulating portion 42 b inthe second direction D2. The second insulating member 42 includessilicon and nitrogen. The second insulating member 42 includes, forexample, SiN. The second insulating member 42 functions as, for example,a protective film. The second insulating member 42 maintains highquality in the second semiconductor region 12.

As shown in FIG. 1 , in this example, the nitride member 31 includes afourth nitride region 31 d and a fifth nitride region 31 e. The firstinsulating portion 42 a is located between the first semiconductorportion 12 a and the fourth nitride region 31 d in the second directionD2. The second insulating portion 42 b is located between the secondsemiconductor portion 12 b and the fifth nitride region 31 e in thesecond direction D2.

In this example, the first insulating member 41 includes the fourthinsulating region 41 d and the fifth insulating region 41 e. The fourthnitride region 31 d is located between the first insulating portion 42 aand the fourth insulating region 41 d in the second direction D2. Thefifth nitride region 31 e is located between the second insulatingportion 42 b and the fifth insulating region 41 e in the seconddirection D2.

Hereinafter, an example of the analysis results of the nitride member 31in the semiconductor device 110 will be described.

FIGS. 2A to 2D and 3A to 3D are images illustrating the analysis resultsof the semiconductor device according to the first embodiment.

FIGS. 2A to 2D correspond to the first nitride region 31 a at the bottomof the recess. FIGS. 3A to 3D correspond to the second nitride region 31b on the side of the recess. FIGS. 2A and 3A are HAADF-STEM ((High AngleAnnular Dark-Field Scanning Transmission Electron Microscopy). FIGS. 2Bto 2D, and FIGS. 3B to 3D are TEM (Transmission Electron Microscopy)-EDX (Energy dispersive X-ray spectroscopy). FIGS. 2B and 3B relate tonitrogen (N). In FIGS. 2B and 3B, the concentration of N in the brightregion is higher than the concentration of N in the dark region. FIGS.2C and 3C relate to Al. In FIGS. 2C and 3C, the concentration of Al inthe bright region is higher than the concentration of Al in the darkregion. FIGS. 2D and 3D relate to Ga. In FIGS. 2D and 3D, theconcentration of Ga in the bright region is higher than theconcentration of Ga in the dark region.

In FIGS. 2A to 2D, the first nitride region 31 a is shown by a brokenline. As shown in FIGS. 2B to 2D, N, Al and Ga exist in the firstnitride region 31 a.

In FIGS. 3A to 3D, the second nitride region 31 b is shown by a brokenline. As shown in FIGS. 3B to 3D, N and Al exist in the second nitrideregion 31 b, and Ga is substantially not observed in the second nitrideregion 31 b.

Hereinafter, an example of the elemental profile in the portionincluding the first nitride region 31 a and the portion including thesecond nitride region 31 b will be described. In the portion includingthe first nitride region 31 a, a change in the concentration of theelement is detected along the Z-axis direction. On the other hand, inthe portion including the first nitride region 31 a, a change in theconcentration of the element is detected along the side verticaldirection Dsx shown in FIG. 1 . As shown in FIG. 1 , the second nitrideregion 31 b includes a first surface F1 facing the fourth partial region11 d. The side vertical direction Dsx is perpendicular to the firstsurface F1.

FIGS. 4A and 4B are graphs illustrating the analysis results of thesemiconductor device in the first embodiment.

These figures relate to the first nitride region 31 a. These figuresillustrate the concentration of elements detected by EDX. The horizontalaxis of these figures is a position pz in the Z-axis direction. Thevertical axis is the detection intensity Int of the element. FIG. 4Ashows the concentrations of Al and Ga. FIG. 4B shows the concentrationsof N, Si and O.

As shown in FIG. 4A, Al and Ga exist in the first nitride region 31 a.Ga and O may be detected in FIGS. 4A and 4B.

FIGS. 5A and 5B are graphs illustrating the analysis results of thesemiconductor device in the first embodiment.

These figures relate to the second nitride region 31 b. These figuresillustrate the concentration of elements detected by EDX. The horizontalaxis of these figures is a position ps in the side vertical directionDsx. The vertical axis is the element detection intensity Int. FIG. 5Ashows the concentrations of Al and Ga. FIG. 5B shows the concentrationsof N, Si and O.

As shown in FIG. 5A, Al exists in the second nitride region 31 b. In thesecond nitride region 31 b, the concentration of Ga (detection intensityInt) sharply decreases.

As shown in FIG. 4A, in the first nitride region 31 a, the peak of thedetection intensity Int of Al is broad, and the detection intensity Intof Ga changes slowly. On the other hand, as shown in FIG. 5A, in thesecond nitride region 31 b, the peak of the detection intensity Int ofAl is sharp, and the detection intensity Int of Ga changes sharply.

For example, in the first nitride region 31 a, a part of Ga included inthe third partial region 11 c may be diffused in the first nitrideregion 31 a. For example, the excess Ga in the third partial region 11 cmoves to the first nitride region 31 a, thereby stabilizing thecomposition in the third partial region 11 c. For example, there arefewer nitrogen vacancies. For example, the crystallinity in the thirdpartial region 11 c is improved. This makes it easier to obtain highercarrier mobility.

For example, by trapping Ga in the first nitride region 31 a, themovement of Ga to the first insulating region 41 a (for example, SiO₂)is suppressed. As a result, a first insulating region 41 a having higherquality can be obtained. For example, higher reliability can beobtained.

As shown in FIG. 4A, there is a distribution of Al concentration alongthe Z-axis direction (second direction D2) in the portion including thefirst nitride region 31 a. The concentration of Al at the first positionpo1 included in the first nitride region 31 a is a peak in thedistribution of the concentration of Al along the second direction D2 inthe first nitride region 31 a. The concentration of Ga in the firstposition po1 is ⅒ or more of the concentration of Ga in the thirdpartial region 11 c.

As shown in FIG. 5A, there is a distribution of Al concentration alongthe side vertical direction Dsx in the portion including the secondnitride region 31 b. As described above, the side vertical direction Dsxis perpendicular to the first surface F1 (see FIG. 1 ). Theconcentration of Al at the second position po 2 included in the secondnitride region 31 b is a peak in the distribution of the concentrationof Al along the side vertical direction Dsx in the second nitride region31 b. The concentration of Ga in the second position po 2 is less than ⅒of the concentration of Ga in the fourth partial region 11 d.

By such a difference in composition between the first nitride region 31a and the second nitride region 31 b, high carrier mobility and stablehigh threshold voltage can be obtained.

The concentration of Ga in the first nitride region 31 a is, forexample, not less than 10 atm% and not more than 30 atm%. Theconcentration of Ga in the second nitride region 31 b is, for example,less than 10 atm%.

From the analysis of the TEM image on the semiconductor device 110, itwas found that there is case where crystallinity differs between thefirst nitride region 31 a and the second nitride region 31 b. Forexample, the crystallinity of the second nitride region 31 b is higherthan the crystallinity of the first nitride region 31 a. For example, inthe first nitride region 31 a, since Ga exists, there is a case wherethe crystallinity is relatively lower than that in the second nitrideregion 31 b. Thereby, the short channel effect can be suppressed moreeffectively.

Ga included in the first nitride region 31 a may be supplied from, forexample, the third partial region 11 c.

FIG. 6 is a schematic cross-sectional view illustrating thesemiconductor device according to the first embodiment.

FIG. 6 is an enlarged view of a part of FIG. 1 . As shown in FIG. 6 ,the first nitride region 31 a includes a first portion p 1 and a secondportion p 2. The first portion p 1 is located between the third partialregion 11 c and the second portion p 2 in the second direction D2. Thecrystallinity in the first portion p 1 is higher than the crystallinityin the second portion p 2. For example, the crystal of the first partialregion p 1 matches the crystal of the third partial region 11 c. Thesecond portion p 2 is affected by the first insulating region 41 a andhas lower crystallinity than the first portion p 1. By such a firstnitride region 31 a, high crystallinity can be obtained in the thirdpartial region 11 c.

As shown in FIG. 6 , the second nitride region 31 b includes a thirdportion p 3 and a fourth portion p 4. The third portion p 3 is locatedbetween the first semiconductor portion 12 a and the fourth portion p 4in the first direction D1. The crystallinity in the third portion p 3 ishigher than the crystallinity in the fourth portion p 4. For example,the crystal of the third portion p 3 matches the crystal of the firstsemiconductor portion 12 a. The fourth portion p 4 is affected by thesecond insulating region 41 b and has lower crystallinity than the thirdportion p 3. By such a second nitride region 31 b, high crystallinitycan be obtained in the first semiconductor portion 12 a.

As shown in FIG. 6 , the third partial region 11 c includes the firstfacing surface FF1. The first facing surface FF1 faces the first nitrideregion 31 a. The fourth partial region 11 d includes the second facingsurface FF2. The second facing surface FF2 faces the second nitrideregion 31 b. An unevenness of the first facing surface FF1 is largerthan an unevenness of the second facing surface FF2.

Large unevenness of the first facing surface FF1 makes it easier for Gato diffuse from, for example, the third partial region 11 c to the firstnitride region 31 a. The concentration of Ga in the first nitride region31 a can be stably increased.

As shown in FIG. 6 , the thickness t1 of the first nitride region 31 aalong the second direction D2 is preferably, for example, not less than1 nm or more and less than 5 nm. When the thickness t1 is 1 nm or more,the first nitride region 31 a being uniform film-like can be obtained.When the thickness t1 is 5 nm or less, for example, control of the breakdown becomes easy. When the thickness t1 is thicker than 5 nm, forexample, influence of the charge trap becomes large.

The thickness t2 of the first insulating region 41 a along the seconddirection D2 is preferably, for example, not less than 5 nm and not morethan 50 nm. When the thickness t2 is 5 nm or more, for example, goodgate insulation reliability can be easily obtained. When the thicknesst2 is 50 nm or less, for example, the electric field distributioncontrol of the gate voltage becomes easy.

As shown in FIG. 6 , the first semiconductor portion 12 a includes thesecond surface F2 and the third surface F3. The third surface F3 facesthe fourth partial region 11 d. The third surface F3 is located betweenthe fourth partial region 11 d and the second surface F2 in the seconddirection D2. The second surface F2 is the opposite surface to the thirdsurface F3. The second surface F2 is, for example, an upper surface. Thedistance along the second direction D2 between a position of the firstfacing surface FF1 in the second direction D2 and a position of thesecond surface F2 in the second direction D2 is defined as a distanced1. The distance d1 is preferably, for example, not less than 0.1 µm andnot more than 1 µm. Thereby, for example, a high threshold voltage canbe stably obtained easily. The distance d1 may be, for example, not lessthan 0.1 µm and not more than 0.5 µm. The distance d1 corresponds to,for example, the depth of the recess.

The above configuration described with respect to the second nitrideregion 31 b can be applied to the third nitride region 31 c.

The first nitride region 31 a and the second nitride region 31 b havingdifferent compositions from each other ss described above can be formedby various methods. For example, a recess is formed in the semiconductormember 10 M, and a film to be the nitride member 31 is formed on thebottom surface and the side surface of the recess by, for example, amethod such as ALD (Atomic Layer Deposition). By partially introducingGa into this film, a region having a high concentration of Ga can beformed. The introduction of Ga into the film may be performed, forexample, by using a gas including Ga at the time of forming the film.The introduction of Ga into the film may be performed by, for example,ion implantation. Alternatively, Al may be partially introduced into thefilm to form a compositional distribution. The introduction of Al intothe film may be performed, for example, by using a gas including Al atthe time of forming the film. The introduction of Al into the film maybe performed by, for example, ion implantation.

For example, the first nitride region 31 a and the second nitride region31 b may be formed by film formation using a mask.

For example, a recess is formed in the semiconductor member 10 M, andthe surface characteristics of the bottom and the side of the recess aremade to be different. For example, the unevenness at the bottom of therecess is made larger than the unevenness at the side of the recess. Afilm to be the nitride member 31 is formed in such a recess. As aresult, at the bottom of the recess, Ga in the third partial region 11 cdiffuses into the film that becomes the nitride member 31. On the otherhand, in the side portion of the recess, Ga is difficult to diffuse fromthe fourth partial region 11 d. Thus, the concentration of Ga in thenitride member 31 may be changed by changing the characteristics of theunderlayer.

Second Embodiment

The second embodiment relates to a method for manufacturing asemiconductor device. The manufacturing method according to theembodiment includes forming a nitride film to be the nitride member 31and introducing one of Ga and Al into a part of the nitride film. Thismakes it possible to form a plurality of regions having differentcompositions in the nitride member 31.

In the embodiment, at least one of the first electrode 51 and the secondelectrode 52 may include, for example, at least one selected from thegroup consisting of Ti and Al. The third electrode 53 may include, forexample, at least one selected from the group consisting of TiN, WN, Ni,Au, Pt and Ti. The third electrode 53 may include, for example,conductive silicon or polysilicon.

Information on length and thickness can be obtained by observing with anelectron microscope. Information on the composition of the material canbe obtained by SIMS (Secondary Ion Mass Spectrometry) or EDX (Energydispersive X-ray spectroscopy). EDX includes, for example, TEM-EDX.

According to the embodiment, it is possible to provide a semiconductordevice whose characteristics can be improved.

In the embodiment, “nitride semiconductor” includes all compositions ofsemiconductors of the chemical formula B_(x)In_(y)Al_(z)Ga_(1-x-y-z)N (0≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, and x+y+z ≤ 1) for which the compositionratios x, y, and z are changed within the ranges respectively. “Nitridesemiconductor” further includes group V elements other than N (nitrogen)in the chemical formula recited above, various elements added to controlvarious properties such as the conductivity type and the like, andvarious elements included unintentionally.

In the specification of the application, “perpendicular” and “parallel”refer to not only strictly perpendicular and strictly parallel but alsoinclude, for example, the fluctuation due to manufacturing processes,etc. It is sufficient to be substantially perpendicular andsubstantially parallel.

Hereinabove, exemplary embodiments of the invention are described withreference to specific examples. However, the embodiments of theinvention are not limited to these specific examples. For example, oneskilled in the art may similarly practice the invention by appropriatelyselecting specific configurations of components included insemiconductor devices such as nitride regions, electrodes, insulatingfilms, etc., from known art. Such practice is included in the scope ofthe invention to the extent that similar effects thereto are obtained.

Further, any two or more components of the specific examples may becombined within the extent of technical feasibility and are included inthe scope of the invention to the extent that the purport of theinvention is included.

Moreover, all semiconductor devices, and methods for manufacturingsemiconductor devices practicable by an appropriate design modificationby one skilled in the art based on the semiconductor devices, and themethods for manufacturing semiconductor devices described above asembodiments of the invention also are within the scope of the inventionto the extent that the purport of the invention is included.

Various other variations and modifications can be conceived by thoseskilled in the art within the spirit of the invention, and it isunderstood that such variations and modifications are also encompassedwithin the scope of the invention.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the invention.

What is claimed is:
 1. A semiconductor device, comprising: a firstelectrode; a second electrode; a third electrode including a firstelectrode portion, a position of the first electrode portion in a firstdirection from the first electrode to the second electrode being betweena position of the first electrode in the first direction and a positionof the second electrode in the first direction; a first semiconductorregion including Al_(x1)Ga_(1-x1)N (0 ≤ x1 < 1), the first semiconductorregion including a first partial region, a second partial region, athird partial region, a fourth partial region, and a fifth partialregion, a direction from the first partial region to the first electrodebeing along a second direction crossing the first direction, a directionfrom the second partial region to the second electrode being along thesecond direction, a direction from the third partial region to the firstelectrode portion being along the second direction, a position of thefourth partial region in the first direction being between a position ofthe first partial region in the first direction and a position of thethird partial region in the first direction, a position of the fifthpartial region in the first direction being between the position of thethird partial region in the first direction and a position of the secondpartial region in the first direction; a second semiconductor regionincluding Al_(x2)Ga_(1-x2)N (0 < x2 ≤ 1, x1 < x2), the secondsemiconductor region including a first semiconductor portion and asecond semiconductor portion, the first electrode portion being locatedbetween the first semiconductor portion and the second semiconductorportion in the first direction, a direction from the fourth partialregion to the first semiconductor portion being along the seconddirection, a direction from the fifth partial region to the secondsemiconductor portion being along the second direction; a firstinsulating member, the first insulating member including a firstinsulating region, a second insulating region, and a third insulatingregion, the first insulating region being located between the thirdpartial region and the first electrode portion in the second direction,the second insulating region being located between the firstsemiconductor portion and the first electrode portion in the firstdirection, the third insulating region being located between the firstelectrode portion and the second semiconductor portion in the firstdirection; and a nitride member including a first nitride region, asecond nitride region and a third nitride region, the first nitrideregion being located between the third partial region and the firstinsulating region in the second direction, the second nitride regionbeing located between the first semiconductor portion and the secondinsulating region in the first direction, the third nitride region beinglocated between the third insulating region and the second semiconductorportion in the first direction, the first nitride region includingAl_(z1)Ga_(1-z1)N (0 < z1 < 1, x1 < z1), the second nitride regionincluding Al_(z2)Ga_(1-z2)N (0 < z2 ≤ 1, z1 < z2).
 2. The deviceaccording to claim 1, wherein the second nitride region includes AIN,and the first nitride region includes AlGaN.
 3. The device according toclaim 1, wherein a concentration of Ga in the first nitride region isnot less than 10 atm% and not more than 30 atm%.
 4. The device accordingto claim 1, wherein a crystallinity of the second nitride region ishigher than a crystallinity of the first nitride region.
 5. The deviceaccording to claim 1, wherein the first nitride region includes a firstportion and a second portion, the first portion is located between thethird partial region and the second portion in the second direction, anda crystallinity in the first part is higher than a crystallinity in thesecond part.
 6. The device according to claim 1, wherein the secondnitride region includes a third portion and a fourth portion, the thirdportion is located between the first semiconductor portion and thefourth portion in the first direction, and a crystallinity in the thirdpart is higher than a crystallinity in the fourth part.
 7. The deviceaccording to claim 1, wherein the third nitride region includesAl_(z3)Ga_(1-z3)N (0 < z3 ≤ 1, z1 < z3).
 8. The device according toclaim 7, wherein the third nitride region includes AIN.
 9. The deviceaccording to claim 1, wherein a part of the first electrode portion islocated between the fourth partial region and the fifth partial regionin the first direction.
 10. The device according to claim 1, wherein athickness of the first nitride region along the second direction is notless than 1 nm and not more than 5 nm.
 11. The device according to claim1, wherein a thickness of the first insulating region along the seconddirection is not less than 5 nm and not more than 50 nm.
 12. The deviceaccording to claim 1, wherein the first insulating member includessilicon and oxygen.
 13. The device according to claim 1, furthercomprising a second insulating member, the second insulating memberincluding a first insulating portion and a second insulating portion,the first semiconductor portion being located between the fourth partialregion and the first insulating portion in the second direction, thesecond semiconductor portion being located between the fifth partialregion and the second insulating portion in the second direction, andthe second insulating member including silicon and nitrogen.
 14. Thedevice according to claim 13, wherein the nitride member includes afourth nitride region and a fifth nitride region, the first insulatingportion is located between the first semiconductor portion and thefourth nitride region in the second direction, and the second insulatingportion is located between the second semiconductor portion and thefifth nitride region in the second direction.
 15. The device accordingto claim 14, wherein the first insulating member includes a fourthinsulating region and a fifth insulating region, the fourth nitrideregion is located between the first insulating portion and the fourthinsulating region in the second direction, and the fifth nitride regionis located between the second insulating portion and the fifthinsulating region in the second direction.
 16. The device according toclaim 1, wherein a concentration of Al at a first position included inthe first nitride region is a peak in a distribution of theconcentration of Al along the second direction in the first nitrideregion, and a concentration of Ga in the first position is ⅒ or more ofa concentration of Ga in the third partial region.
 17. The deviceaccording to claim 1, wherein the second nitride region includes a firstsurface facing the fourth partial region, a concentration of Al at asecond position included in the second nitride region is a peak in adistribution of the concentration of Al along a side vertical directionin the second nitride region, the side vertical direction isperpendicular to the first surface, and a concentration of Ga in thesecond position is less than ⅒ of a concentration of Ga in the fourthpartial region.
 18. The device according to claim 1, wherein the z2 ishigher than the x2.
 19. The device according to claim 1, wherein the x1is not less than 0 and less than 0.1, and the x2 is not more than 0.1and not more than 0.5.
 20. The device according to claim 1, wherein thethird partial region includes a first facing surface facing the firstnitride region, the fourth partial region includes a second facingsurface facing the second nitride region, and an unevenness of the firstfacing surface is larger than an unevenness of the second facingsurface.